good evening Pisces20! My mother in law mentioned to me about your chameleon and I thought i should post as soon as possible.
First i have a few questions..
1. What are you dusting your crickets with and what are you gutloading your crickets with?
-It is VERY important that your chameleon gets the right vitamins and such that is needed. I strongly Suggest the Product REP-CAL. for both the Calcium with vitd3(PINK LABEL) and Herptivite multivitamins(BLUE LABEL).You also have to be sure to gut load your crickets or eles they have NO nutritional value to yoru chameleon at all.
2. What lights do you have all together?
-Again this is important for your chameleon to digest the food and to absorp the vit d. JUST LIKE HUMANS...We use the REPTI-SUN 5.0 uva/uvb light..A PLAN UV LIGHT IS NOT ENOUGH!.Also you need to have at least one heat light with approx a 100 watt bulb or something that keeps temps between 85-95 degrees during the day and approx.65 at night.
3.Other than misting do you use a dripper system of some sort?
-Be sure that your humitity is above 50.you can get both humitity and temp gauges at your local pet store if you don't have them already.

Now to answer some of your questions
A chameleon missing the prey is not always something to worry about, but when its happening alot its called LAZY TONGUE. this happens when a chameleon is feed by hand/cup and they don't have to work for the food, its good "tongue exercise" for them to have to chase down the food and it makes them work the tongue. if you hand/cup feed there is nothing wrong with it and in fact we do it as well but we tend to feed her some that way and then dump the rest in her cage for her to look for, this works well for us.
Its difficult to find a vet and can be costly but with the problems that your mentioning with him being weak i would really suggest a vet visit. Im not the most experinced but from the things you have mentioned it does kinda sound like something i heard called MBD. i often visit a reptile site called www.petreptiles.com THEY ARE WONDERFUL THERE i do hope you check it out there are very many wonderful owners with so much information to share so please visit us there and i hope this helped you..
GOOD LUCK AND PLEASE KEEP UPDATING US ON YOUR PROGRESS AND SOME PICTURES!
SLICKS_MOMMA